Circuit breaker



May 22, 1945. L. w. DYR- ET AL C IRCUIT BREAKER Filed oct. so, 1942 2 Sheets-Sheet 1 INVENTOR5 WITNESSES;

z am w m py m f Z ZM May 22, 1945 1 w. DYER ET AL CIRCUIT BREAKER Filed Oct. 30, 1942 2 Sheets-Sheet 2 f n E u Vy 7 w3 Illlll f 5 m a o/a Nal., 7 9 7 9 i U w 7, G 2 9 3 B l@ w 5 9/ ll HV. 7 M ll l 5 H l 9 F/ 3 H H H n m QQ f//./u L bm 54 3 7 9 n Z z M .0 ,n m n u m f WITNESSES:

` lNvENToRs ./oyohpyef and /L//V/erPar//marn BY 1;/ q) ATTORNE Patented May 22, 1945 CIRCUIT BREAKER Lloyd W. Dyer, Wilkinsburg, and Hiller D. Dorfman, Forest Hills, Pa., assgnors to-Wcstinghouse Electric & Manufacturing Company,

East PittsburghQ Pa., a

Sylvania corporation of Penn- Applieauon october 3o, i942, serial No. 463,935

(ci. aco-mss) l2 maints.

The invention relates to circuit interrupters and, more particularly, to circuit breakers of the type that are automatically tripped open after a time delay in response to predetermined over load current conditions up to a certain maghin tude and that are tripped open instantaneously upon the occurrence of heavy overloads or short circuits.

An object of the invention is the provision of an improved circuit breaker of the class described which is very simple and compact, accurate and reliable in operation, and economical to manufacture.

Another object ofthe invention is the provision of an improved circuit breaker of the class described which is substantially shock-prooi, that breaker latch to trip the breaker is produced by a spring actuated trip member which is normally latched in inoperative position by the armature member of the previously described electromaglar in the appended claims.

netic tripping means.

'llhe novel features that are considered characteristic ci? the invention are set forth in particu The invention itself, however, both as to structure and mode of oper ation, together with additional objects and advantages thereof, will be best understood from the is, it will not be falsely tripped by shocks or jars even though the breaker may be carrying the full rated current or even slight overload current.

Another object of the invention is the provision of a circuit breaker having an improved thermalmagnetic trip device wherein tripping of the breaker is controlled jointly by an 'electromagnetic tripping means and a current responsive bimetal element so arranged that the breaker will not be falsely tripped by shocks or lars.

Another object of the invention is the provision oi a circuit breaker with an improved trip device comprising lan electromagnetic tripping means operable to cause tripping of the breaker, and a current responsive bimetal element having an edge portion normally disposed in a blocking position directly in the path of movement-,of a part movable with the amature of the magnetic means to prevent tripping operation thereof except in response to predetermined overload conditions, the said blmetal element when heated a predetermined amount by overload current denecting transversely of the plane of movement of the magnetic means to a non-blocking position to thereby permit tripping operation of the magnetic means.

Another object of the invention is the provision of a circuit breaker with a trip device as previ ously described, wherein the bimetal element is normally disposed in blocking position directly in the path of movement o1' a dat leaf spring carfollowing detailed description of one embodi ment thereof when read in conjunction with the accompanying drawings, in which: Figure l is a front elevational view, partly in section, of a multi-pole circuit breaker embody ing the features ofthe present invention;

idg. 2 is a vertical sectional view of the circuit breaker taken substantially adjacent the center pole thereof, the parts being shown in the closed circuit position;

liig. 3 is an enlarged fragmentary sectional view illustrating an instantaneous tripping operation of the trip device, such as is produced by a heavy overload or short-circuit condition in the circuit through one of the poles of the circuit breaker;

our copending application for Shock-,proof cir# cuit breakers, Serial No. 463,934, lled October 30, 1942, and assigned to the assignee of the present invention.

Referring to Figs. 1 and 2 ofthe drawings,

the base 'I of the circuit breaker is of molded insulating material and has mounted thereon six t terminals 9, two foreach of the three poles of rled by the armature of the electromagnetic tripping means, the spring being designed to permit instantaneous tripping operation of the -armature upon heavy overloads and short circuits irrespective of the position of the bimetal element.

Another object of the invention is the provision' of a circuit breaker with an improved trip device wherein the force for releasing the circuit the circuit breaker, three stationary contacts il, and arc-extinguishing device I3 foreach of the three poles, a circuit breaker operating mechanism l5 which has associated therewith the three movable switch members l1, and a trip device indicated generally at I9 ,for controlling automatic operation of the circuit breaker. A cover 2| is removably secured to the-base 1 and cooperates therewith to form a casing for enclosing the circuit breaker mechanism. The base and cover are each provided with apluralityof barriers .the manual operating handle.

which serve to divide the casing longitudinally into three compartments, one for each pole of the circuit breaker.

Each of the switch members I1 includes a resilient switch arm 23 preferably of spring steel which is riveted at one end to the associated s witch member frame 25. 'Ihe other end of the spring contact arm carries a movable contact 21 which is adapted to be moved into and out of engagement with the stationary contact II. A ilexible shunt conductor 29 is provided for .connecting each of the movable contacts 21 with a corresponding one of the conducting straps 3l which serve to complete the electric circuit from the shunt conductor 29 to the corresponding .pole of the trip device I9. Thethree switch member frames 25, which are substantially U-shaped, are rigidly mechanically connected together by means of an insulating tie bar 33 which extends through suitable openings in the sides of the switch member frames, the tie bar being rigidly fastened to each of the frame members 25 by Cil means of a clamping strap. Each stationary 'i contact II is vmounted on the inner end of a corresponding conducting strip 35 which is secured to the base 1 by means of screw 31. The

outer end of this conductor strip 35 is electrically l terminal 9.

The' operating mechanism I5 which is of the quick-make and quick-break type is supported on a U-shaped main frame 39 mounted in the center pole compartment of the circuit breaker and secured to the base 1 by means of screws 4 I. The operating mechanism comprises a bifurcated operating lever 43, a toggle comprising toggle links 45 and 41 for engaging the interconnected switch members I1, a pair of overcenter springs 49 for operatively connecting the operating lever 43 with the knee pivot pin 5I of the toggle linkage, and a supporting lever or cradle 53 for supporting yone end of the toggle linkage so as to provide a means whereby actuation of the trip device I9 can cause the operating mechanism to automatically move all of the switch members I1 to open circuit position irrespective of the position of The bifurcated operating lever 43 is pivotally supported on the sides of the U-shaped frame by means of two pivot pins 55 (only one being shown) An operating handle 51 is secured to the outer end of the operating lever 43 to provide for manual operation of the circuit breaker. This handle has a knob portion which ,projects through an elongated slot provided therefor in the cover 2|, and is also provided with an arcuate shield portion 59 for closing the handle slot in all positions of asf/arse ical connection between the operating mechanism and the assemblage of switch members. The other end of the inner toggle link dl is pivotally connected to the inner end of the other toggle link 45 by means of the knee pivot pin 5l This knee pivot pin extends for some distance on either side of the pivotally connected toggle links and each of the projecting ends is adapted to be engaged by one end of the overcenter springs G9, the other end of the operating springs being fastened to the central portion of the bifurcated operating lever` 43. The outer end oi;-` the toggle link 45 is pivotally connected by a pivot pin 65 to the carrier lever or cradle 53, which, in turn, is pivotally supported on the U-shaped main frame 39 by means of a pivot pin 66. The limits of motion of the operating' lever 43 are defined by offset projections of the sides of the main frame 39.

The cradle or carrier lever 53 is normally adapted to be held in the latched position shown in Fig.' 2 by means of a latch of the trip device, and in this latched position the cradle forms a iixed support for the outer end of the toggle linkage so that the circuit breaker may be manually opened and closed by means of the operating handle 51. When the circuit breaker is in the closed position shown in Fig. 2, the three switch members are held locked in closed position by the overset relation of the operating toggle 45, 41 as long as the cradle 53 is held in latched position. In this position, the overcenter springs 49 act to maintain the operating handle in the on position and also bias the operating toggle to its overset locking position. The cradle 53 is always biased in a clockwise direction as viewed in Fig. 2, by a component of the force of the overcenter springs, and when this cradle is released by the operation of the trip device, the assemblage of thethree movable switch members is quickly actuated to open position by means of the overcenter springs. Upon such release, the cradle 53 is rotated in a clockwise direction, as viewed in Fig. 2, and as soon as the axis of the pivot pin 65 is shifted to the right of the line of action of the overcenter springs 49, the operating toggle is caused to collapse, and the operating handle is moved to an intermediate indicating position. Be-

fore the breaker can be again closed, it is necescludes a rotatably supported trip bar 1I of molded insulating material which has a centrally disposed shaft 13 molded therein. The trip bar is provided with three T-shaped projecting members 15 formed integral therewith and sixannular slots for supporting the three spring actuated trip members 11, there being one projection 15 and one trip member 11 for each of the three poles oi the circuit breaker. The trip bar is also provided with a means for engaging and latching the cradle 53 of the circuit breaker operating mechanism.A This engaging means comprises a latch 19 rigidly affixed to the trip bar and having spaced sides which are joined by a latch portion 8|, which is adapted to engage and latch the free end of the cradle 53. The latch 19 also carries a cross-pin'83 between its sides, and this pin provides means whereby the trip device is reset by estense the cradle t@ when the cradle El is manually reset to lstchine position by means of the operating; die l'. 'l'lie trip bar li is rotatably supported on e noir oi opeten bracket members it se cured to the loose 'i adjacent the opposite side wells thereof. The outer ends of the bracket members it ore connected by en insilietine roti ci tvnicn forms e, support ier one enel ot they iriyninc springs @il which. individunlly biss end estinto tire trio members ll to the tripped :cosic- I, tion., o the spring sctueted trio meinbere the trin bor so to be indiviclnolly niovoble Tire enculer slots in the trio ond the cenit-circuler beering slots oi tno trio mein bers oi substentisliy the sence rediris so that movement oi the spring actuated trip meno here is essentially one of rototicn shout tire eine oi tite trinlocr itself. Eecli of the trin menfibers is bisserl in e counter-clockwise direction es vievveol in 2', by tivo ci tice springs Sii, so that when one o tire trip members is releosed, it will e. corresnondine one oi the projections 'lil ond ectnete the trip ber 'di to trinned position to trip the circintbreelrer.. The snececl sides ci econ trip member 'il ere disposed directly over the =nortion ci e. corresponding one ci tire projections l5 on the trip loer il so tient tire edges oi tl'iese side portions wili enges@ tlie nroiection enti move the trio bor when time trio niemeer is releeeed. Esch oi the three trip members 'lil carries en cdinstcble loten niece ci orienten to be eneeeecl by o loten to restreintne trin member in the interred position shown in Fie. 2..

The circuit breaker contacts, operating moche cisne, onli tiret portion of the trip device tient "nos been described in theprecedine noroeroloh ere sulostnntiolly similor to the corresponding ports oi' tbe circuit breelxer disclosed in Potent lilo. Zilui, issued to ll. D. Dorimen, August li, loto, ond cscienerl to the assignee o1? the present invention. The remaining portions oi? the trln device, however, ere oi:` entirely dinerent con struction and have e different inode oi coercition ,from the trip structure shown in the aforementioneol Patent No. 2,050,285.

it is very importent, especially in opplicntions ci circuit breakers where vibrotions ond severe jars or shocks ore encountered, thelt the circuit breaker should not falsely trio own in response to such vibrations. jars, or shocks. The moin source of trouble which causes the circuit breaker to be falsely tripped by vibrations, jars, orshocksusually resides in the electroeresponsive trip ele= ments, such as' the electrommagnetic tripping means ond the thermally responsive trip elements, since these elements ore usually very sensitive to shocks. trip bar can very easily be made substantially shock-proof by various known methods. cordance with the present invention, each. pole of the circuit breaker is provided with an imn proved electro responsive tripping means of very simple and reliable construction, in which the parts thereof are so arranged as to makethe circuit breaker substantially shock-proof. The oonstruction of each electro-responsive tripping means is such that it aiords a time delay action before tripping the breaker in response to over- The main circuit breaker latch and the loods np to e predetermined magnitude, sind oleo enects instentoneous tripping of tiie circuit breaker upon the occurrence ci heavy overvloede or snort circuits in the circuit ci' any pole of brenner. llech electro-responsive tripping ineens comprises on eieetro-msgnet indicetecl generally et end e current responsive bimetel element each energized in response to the current of the circuit of :its corresponding pole. The elec@ trournngnet comprises o ilnsiisped stations oi magnetic materiel, en energizing wir upon the shorter leg of tine stetih ery core, sind on fermeture member iti vJi l nivoted intermediete its ends by e. nivot the longer leg of the stationery core., il e tionery core is secured by rivets to e, iii-vii supnorting freine its, which is, in turn, seein to tbe hose l of tire circuit breeirer by ser v iili. A iinrtieneii loten element it@ is secured to tlie extension ci? the aermoture member iti ndice cent the outer end thereof, snol this latch element is coloni-,ed to entrego the letcl'i piece @i of o. cor@ responding one' ci the spring ectuetecl trio wenn bers to hold the trip member in the latch-.ed position shown when the erinnture member i i is in its nnottrncted position. el reletiveiy strong niet leef iii is rigidly Secured et its inner enti to the armature member lili adjacent the inne-.c enel oi? the ermstnre member. The lect spring iii is .slightly oset end n roeier portion thereof en is in spoced relation substentioily nerollei to the ermoture member, and e cylindri col inten niece itil is secured to the outer tree enel ot the lest spring. guide pin i iii secured to the erinoture member itil extends loosely through en opening provided therefor in the lecci spring,r iiil to prevent any suhstontisl interni clisplncement of the leef spring ill .relative to the ermetine member. in ecljusting screw ill is threaded through on intermediete portion of the leef spring iii end engages the armature member iti. The purpose o 'this adjusting screw is to provide s. means for adjusting the strength or torce oi' the lent spring iii to thereby ndjust the inctentnneous tripping point ci? the electronics netic trigo ineens. A relatively light biasing spring il@ is connected at one end to the lovvei` end of the ermoture member lili and the other enel oi this hissing spring is anchored to e fixed insulatine plete iti secured to the bracket which son ports the bimetel element The current responsive bimetal element @il comprises o not strip of bimetellio materiel winch is rigidly secured and electrically connected et lower end to e. supporting termine/l bracket which is, in turn, ysecured to the base by ineens, of n screw itt threededly engaged in on insert molded in the bose o the bresker, The bimetsi strip is mounted with its rflot side substantially in the pinne oi' lmovement of the armature mem= loer iti so thot one oi the edges of the outer end of the bimetnl strip is normally disposed in block ing relotion directly in the path of movement of the lotch piece i it carried by the free end o the leaf spring lli on the armature member iti. The edge portion of the bimetal strip opposite the edge which engages the latch 4piece H3 rests against and barely touches a. cross-portion mi oi the U-sheped frame 105., The free end of the bimetal strip' 95 is electrically connected byed .flexible shunt conductor |29 to one of the end terminals il ofthe corresponding pole. of the circuit breaker, andthe inner or base end of the bimetal strip is electrically connected to one end of the winding 8.8 of the electro-magnet by the mined magnitude or on short circuits` terminal bracket I23. The other end of the energizing winding is electrically connected by a conductor I3| to the terminal strip 3l which is connected to the movable contact 21. It will thus be seen that the bimetal strip 95 and the energizing winding 99 of the electro-magnet are connected in series with the contacts of the corresponding pole of the circuit breaker so as to be responsive to the current of the circuit of the corresponding pole.

lThe current responsive bimetal element 95 normally, that is, during normal current conditions, acts through the relatively strong leaf spring III to maintain the armature member IIJI in the unattracted latching position, in which it holds the spring actuated trip member 'I1 in latched position. The bimetal element 95 is designed so that it will bend or deflect when heated a predetermined amount by overload currents in excess of the predetermined value, for' example, in excess of 125% of the normal rated current of the breaker. When heated a predetermined amount by such overload current, the bimetal/strip deilects in a direction 90 transverse to the plane of movement of the armature member IUI to a non-blocking position in which the outer end of the bimetal disengages the latch piece H3 carried by the leaf spring I I I, so that it thereby permits the electro-magnet to operate the armaturel member IIlI to attracted position, as shown in l,

Fig. 4, to release the spring actuated trip member il and effect tripping of the circuit breaker. In this instance, the electro-magnet does not have to overcome the opposing force of the relatively strong leaf spring II I in moving the armature to attracted position. The electro-magnet is so designed that it will develop suflicient tractive force to operate the armature to attracted position and release the trip member 'I1 when overload current through its corresponding pole exceeds a prede- L termined magnitude, preferably the same minimum magnitude that will ultimately produce suiiicient heat to deflect the bimetal element 95, that is to say, for example, 125% or more of the normal rated current of the breaker. yCurrents below the predetermined magnitude will not produce sufcient force to ac tuate the armature to attracted position even though the bimetal element has disengaged the latch piece of the leaf spring. The tiine required to heat the bimetal strip 95 a predetermined amount suiiicient to cause it to unlatch the armature member provides a time delay in the tripping operation of the breaker which varies inversely as the current of the circuit, that is to say, the-higher the overload current the shorter the time delay before tripping of the breaker will occur.

The electromagnet 93 is also operable to cause instantaneous tripping of the breaker upon the occurrence of heavy overloads above a predeterlor this purpose, the leaf spring is designed, or its strength is adjusted by means of the screw i Il, so that the pull of the electromagnet will be sufficient to overcome the strength of the spring I l i and actuate the armature lill to attracted position upon the occurrence of overloads in excess of predetermined desired value, for example, in excess of 10 to l2 times the normal rated current of the circuit breaker. Instantaneous tripping will occur under such conditions even though the bimetal element 95 has not had sufficient time to heat up and deflect to non-blocking position, because the pull of the magnet will be sufficient under such conditions to move the armature IDI to attracted position against the force of the leaf spring III, even though the free end ot the leaf spring is held in latched position by the bimetal element.

The electro-responsive tripping means of the other poles of the breaker are identical to the one that has just been described.

A plurality of springs |35 engage the underside of the trip bar projections l5 and act to bias the trip bar to its latching position. The trip bar is preferably constructed so that it is balanced with respect to its center of rotation, and hence will not be moved by vibrations, jars or shocks. Moreover, the line of action of the i'orce exerted by the springbiased cradle 5I on the trip bar passes through the axis of rotation of the trip bar, so that this force does not tend to rotate the trip bar in either direction. The main breaker latch le is strongly held in latching position not only by the latch load produced by the overcenter operating springs 49 acting through the cradle 53, but also by the relatively strong frictional forces of the three trip members 11 which are pressed rather stronglyA against the trip bar when the three trip members are held in latched position by the armature members IUI. The construction of the electro-responsive tripping means is such that it is made substantially shock-proof so that it will not be falsely operated by vibrations, jars or shocks. This is due to the fact that the armature members IIII are strongly held in latching position by the relatively strong leaf springs III which are, in turn, held against movement by the blocking effect of the current responsive bimetal elements 95. The armature members IDI are preferably pivoted as near their center of gravity as possible so as to minimize the possibility of these members being moved by shock. Any vibration, jar or shock in e, direction which might tend to move the armature members IOI to attracted position is resisted and prevented by the relatively strong leaf springs Il and by the blocking effect of the bimetal elements 95 which are immovable in the tripping direction of the armatures IUI. Lateral shocks which might move the bimetal elements 95 to non-blocking position, will not cause tripping of the breaker since such forces are not in such a direction as to produce movement of the armature members Inl.

The operation of the circuit breaker is briefly as follows: The circuit breaker is shown in Fig. 2 in the closed circuit position, the trip device being in the untripped position- To open the contacts manually, the operating handle 51 is moved in a counter-clockwise direction to the off position'. This movement brings the line of action of the springs I9 to the left of the pivot axis 65, thereby causing the operating toggle to be moved to a collapsed position and effect movement of the three movable switch members I1 to open position. To close the contacts, the operating handle is moved from the 01T position in a clockwise direction back to the on position shown in Fig. 2. This movement of the handle shifts the line of action of the springs to the right of the axis of the pivot pin t5 and thereby causes the springs to actuate the operating toggle to its overset position to effect movement of the three movable switch members i'l to closed position.

Upon the occurrence of an overload above the minimum trip setting of the device in the circuit controlled by any of the poles of the breaker, the corresponding current responsive bimetal element 95 is heated by such overload current and when heated a predetermined amount deiects to a nonassorto blocking position, in which it is disengaged from disposed out oi the path of movement oi the latch piece lit carried by the leaf spring ill. This releases the electro-magnet for operation, whereupon the electro-magnet moves the armature' member iti to attracted position to thereby effect release ol the corresponding spring actuated trip member 'il'. Upon release, the spring actuated trib member engages the corresponding T- shaped projection iti on the trip bar and rotates the trio bar to tripping position to disengage the main circuit breaker latch it) from the cradle dit.

The operating springs i9 thereupon actuate they three movable switch members to operi position cause collapse ci the ,operating toggle irrespective ot the position oi the operating handle This time delay tripping operation oi' the trio device is illustrated in Fig. d.

@Joon the occurrence or a largeoverload or short circuit condition in the circuit controlled 'oy any one oi the poles of the breaker, the corre spending electro-magnet @il will be euergised a sufficient amount thereby to operate the armature member iti to attracted position agaimt the :torce of the leaf spring iii, even though the bi metal element has not had time to move to :ionbioclriug position. The operation oi the armature lili to attracted position eilects tripping of the that is, without any timev delayractiori such as would occur ou lower overloads uo to the prede termined instantaneous tripping point. Tripping operation or the trip device ori heavy overrloads or short circuit conditions is illustrated in Fig.

Following each tripping operation of the brealrer, it is necessary to restore the operating mechariism to au operative condition. This is done by moving the operating handle lill in a counterclockwise direction as iar as it will go in the ofi direction. This movement or the operating haridle is transmitted to the cradle td through the projection di. As the cradle is rotated in the resetting direction, the free ehd thereof engages the cross-pin ori the circuit breaker latch l@ and moves the trip bar and latch in a clockwise direction a sumcient distance to permit the latch portion iii to reengage the free end of the cradle This reengagement occurs somewhat before the operating handle reaches the limit of its motion. The rotation ci the trip bar back to its reset latching position not only effects reengaging of the cradle but in addition, it acts through the T-shaped projections 'l5 to reset any of the spring actuated trip members il that have been released, thereby restoring the spring actuated trip members to their latched position, in

4which they are engaged by the latches of the armature members ii. The biinetal elements ad when cooled, return to their normalblking position.` The circuit breaker mechanism is thus I reset and the circuit breaker may be again closed by moving the operating handle to the on'f position. l

Although the invention has been illustrated as I and combinations ci? elements may be made with out departing from some oi.' the essential i'eahm'es of the invention. It is desired, therefore, that the language oi the appended claims should be givers as reasonably broad an interpretation as the prior y tion directly in the path of movement of said. spring Abiased member to normally prevent movem i ment of said armature tc attracted position, acid bimetal element when heated a predeterimued amount deflecting to a nou-blocking position out of the path of movement oi said part to thereby permit operation oi said armature, and said him metal element being disposed so that it is able only in a direction. transverse to the clame of movement oi said. armature.

In a circuit breaker of the class described having, in combination, relatively movable cori-z tacts, operating mechanism therefor, trio device comprising a trip element operable cause a tripping operation of said mechanischen electro magnet energized by the current oi' the circuit for operating said trip clement in response to prem determined overload conditions, and a generally flat current responsive bimetal element mounted i with its dat side substantially in the blaue ot movement of said trio element and having a lorrgitudinal edge portion normally disposed in biocliing relation directly ih the path of movement oi? a part movable with said trip element to thereby normally prevent operation of said trip element, a fixed member barely touching the opposite lem gitudinal edge portion oi the bimetal element. and said bimetal element when heated a predetermined amount deecting irl a direction transll verse to the plane of movement of said. trio ele ment to a nonblocking position to thereby nermit operation of said trip element` 3. In a circuit breaker of the class described having, in combination, relatively movable con tacts, operating mechanism therefor including e. spring actuated member releasable to cause operi ing of said contacts, a trip device comprising an electromagnet having an armature operable to an attracted position in. response to predeterf mined overloadconditions to cause rcleas'e'of said spring actuated member, a spring biased member extending generally parallel to said armature and movable therewith and also relative thereto, and a current responsive bimetal element having a longitudinal edge portion normally disposed in. blocking relation directly in the path of movement of said spring biased member'to normally prevent operation of said armature, said blmetal element when heated a predetermined amount deectiug in a. direction transverse to the plane of movement of said armature to a non-blocking position to thereby permit operation of said armature.

4. In a. circuit breaker of the class described having, in combination, relatively movable contacts, operating mechanism therefor including a spring actuated member releasable to cause opening of said contacts, an electromagnet energized by the current of the circuit having an armature biased to a normal position in which it latches said spring actuated member and operable by the electromagnet to an attracted position in response to predeterminedoverload conditions to release said member, and a current responsive bimetal element having a longitudinal edge portion normally disposed in blocking relation directly in the path of movement of a part carried by said armature to thereby normally prevent movement of said armature to attracted position, a fixed member barely touching the opposite longitudinal edge portion of the bimetal element, and said bimetal element being heated in response to the current of the circuit and when heated a predetermined amount by overload current defiecting in a direction transverse to the plane of movement of said armature to a non-blocking position to thereby permit operation of said armature.

5. A circuit breaker of the class described having, in combination, relatively movable contacts,`

operating mechanism therefor, a trip device comprising `an armature element operable to cause said mechanism to automatically open said contacts, resilient means including a member carried by said element generally parallel thereto, an electromagnet energized by the current of the circuit and operable in response to predetermined overload conditions to operate said armature element, and a current responsive bimetal element extending generally parallel to said member of the resilient means and normally disposed in blocking relation directly in 'the path of movement of said resilient means so as to normally prevent operation of said magnetically actuated element except when said electromagnet is energized sufficiently to overcome the tension of said resilient means, said bimetal element being disposed ,to deflect only in a direction transverse to the plane of movement of said magnetically actuated element, and said bimetal element when heated a predetermined amount defiecting to a non-blocking position out of the path of movement of said resilient means to thereby permit said electromagnet to operate said magnetically actuated element without overcoming the tension of said resilient means. 4

6. A circuit breaker of the class described having, in combination, relatively movable contacts, operating mechanism therefor, a trip device comprising an electromagnet energized by the current of the circuit and having a'n armature movable vto an attracted position in response to predetermined overload conditions to cause tripping of said operating mechanism, a spring carried by said armature, a current responsive bimetal element having an edge portion normally disposed in blocking relation directly in the path of movement of said spring to normally prevent operation of said armature except when said electromagnet is energized sufliciently to overcome the tension of said spring, said bimetal element being prising an electromagnet energized by the current of the circuit and having an armature member operable to an attracted position in response to predetermined overload conditions to cause said mechanism to automatically open said contacts, a leaf spring carried by said armature member, and a current responsive bimetal element having an edge-portion normally disposed in blockingr relation directly in the path of movement of said v leaf spring to normally prevent operation of said armature member except when said electromagnet is energized suiciently to overcome the tension of said leaf spring, Said bimetal element being heated in response to overload currents and when heated a predetermined amount deecting to a non-blocking position out of the path of movement of said armature member to thereby permit said electromagnet to operate said armature member without overcoming the tension of said spring.

8. A circuit breaker of the class described having, in combination, relatively movable contacts. operating mechanism therefor, a trip device comprising an electromagnet energized by the current of the circuit and having an armature member pivoted intermediate its ends and operable to an attracted position to cause said mechanism to automatically open said contacts, a leaf spring carried by said armature member, a second spring engaging said armature member for biasing said member to unattracted position, and a current responsive bimetal' strip mountedA with its iiat side substantially in the plane of movement of -said armature and having an edge portion normally disposed in blocking relation directly in the path of movement of said leaf spring to normally prevent operation of said armature member except when said electromagnet is energized a suflicient amount to overcome the tension of both -springs, said bimetal element being heated in response to overload currents and when heated a predetermined amount defiecting transversely of the plane of movement of said armature member to a non-blocking position to thereby permit said electromagnet to operate said armature without overcoming the tension of said lear spring.

,9. A circuit breaker of the class described having, in combination, relatively movable contacts, operating mechanism therefor, a trip device comprising an electromagnet having a, pivoted armature member movable to an attracted position to cause said mechanism to automatically open said contacts, a leaf spring secured at one end to said armature, a current responsive bimetal element having an edge portion normally disposed in blocking relation directly in the path of movement of said leaf spring to normally prevent operation of said armature except when said electromagnet is energized a suflicient amount to overcome the force of said spring, said bimetal element being heated in response to overload current and when heated a predetermined amount defiecting to a non-blocking position out of the path of movement of said spring to thereby permit operation of said armature without overcoming the force of said spring, and means for adjusting the force of said spring.

l0.' A circuit breaker of lthe class described having, in combination, relatively movable contacts, operating mechanism therefor, a normally restrained spring actuated member operable when released to cause automatic opening operation of said contacts, an electromagnet having an armature member operable to an attracted position in response to predetermined overload conditions to cause release of said spring actuated member, 'a leaf spring carried by said armature member, and a bimetal element having an edge portion normally disposed in blocking relation directly in the path of movement of said leaf spring to nor mally prevent operation of said -armature except when said electromagnet is energized sufficiently to overcome the force of said spring, said bimetal element when heated a predetermined amount defiecting in a direction transverse to the plane oi movement of said armature member to a non blocking position to thereby permit operation of said armature by said y electromagnet without overcoming the force of said leaf spring.

11. In a multi-pole circuit breaker of the class described having, in combination, a plurality of sets of separable contacts, an operating mechanlsm therefor including a single normally re strained spring actuated member operable when released to cause automatic opening of said plurality of sets of contacts, a trip bar operable to eifect release of said spring actuated member, a plurality of electromagnets each having an armature operable to an attracted position in response to predetermined overload conditions and said its corresponding armature to non-blocking poarmatures comprising the only means acting di rectly to actuate said trip bar, a. leaf spring carried by each armature, and a separate current responsive bimetal element for each of said armatures having an edge portion normally disposed in blocking relation directly in the path of movement of the leaf spring of the corresponding armature to normally prevent operation of said armature except when the corresponding electromagnet is energized sufficiently to overcome the tension of said spring, each bimetal element when sition to thereby permit operationof said arma- 'ture by said electromagnet without overcoming the force of said leaf spring.

12. In a circuit breaker of the class described having, in combination, relatively movable contacts, operating mechanism therefor, a normally restrained spring actuated member operable when released to cause said mechanism to open said contacts, an electromagnet having a pivoted armature member biased to a normal position in latching engagement with said spring actuated member to restrain the same and operable to an attracted position in yresponse to predetermined overload conditions to release said member, a leaf spring carried by said armature member, and a current responsive bimetal element having an edge portion normally disposed in blocking relation directly in the path of movement of said spring to normally prevent operation of said armature except .when vsaid electromagnet is energized sufficiently to overcome the force of said leaf spring, said bimetal element when heated a predetermined amount deliecting in a direction transverse to the plane ofmovement of said armature member to a non-blocking position to thereby permit said electromagnet to operate said armature member without overcoming the force of said leaf spring.'

LLOYD W. DYER.

HILLER D. DQRFMAN. 

